DESCRIPTION: This project seeks to rapidly advance the state of the art in understanding and discovering new therapeutic agents for the treatment of traumatic injury to cartilage. Excessive loads and blunt force trauma are responsible for initiating and furthering cartilage pathology and eventually an under repaired joint surface that progressively deteriorates and functionally fails. Indeed, patients with focal cartilage defects have quality of life scores comparable to those with severe osteoarthritis (OA), further emphasizing the need for early intervention. Post-traumatic OA (PTOA) defines the subset of OA patients whose cartilage pathology emerged directly as a consequence of trauma to the joint and in fact probably started with the traumatic injury to the joint. PTOA is widespread in both the general and military population, and is largely untreatable and untreated in current clinical practice. The challenge in cartilage repair after such injuries i the inherent poor healing capacity of the native tissue and the lack of molecules that can be used at the time of injury to preserve cell viability, biosynthetic activities, and foster intrinsi repair. Moreover, there is currently no high throughput screening method that models this injury state, and so no clear route forward for the rapid identification of novel therapeutics that could improve clinical practice and patient outcomes after injury. Our design platform is centered on the development of cartilage- like tissues on the micro-scale and in large quantities. We then mechanically impact these cartilage tissue analogs (CTAs) and assess their cellular and overall degenerative response as a function of time subsequent to insult. In Aim 1 of this proposal, we will scale up an existing validated high throughput testing system to accommodate even larger sample numbers and develop rapid and cost effective outcome measures specific to degradative signaling in cartilage after injury, thus making the testing platform suitable for high throughput screening (HTS). In Aim 2, we will validate this novel device in conjunction with engineered CTAs and native tissue, so as to match the timing and magnitude of key signaling events that occur after injury. In Aim 3, we will use this validated system to screen commercially available small molecule libraries in order to identify molecules important in chondrocyte response to injury. In Aim 4, we will use both soluble and biomaterial-mediated delivery systems in order to test the therapeutic efficacy of identified compounds (and their combinations) in human tissue analogs and native human cartilage response to injury. These delivery systems are designed to enable rapid translation to subsequent pre-clinical animal models and ultimately to human clinical trials. The study is highly translational in that it relates to the all too commo instance of blunt force trauma and injury to cartilage, a condition extremely prevalent in the active duty military population, and will provide a novel and much needed testing platform for small molecule discovery in this clinical domain.